<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>


<script>
    function Foo(){
        Foo.a = function(){
            console.log(1);
        }
        this.a = function(){
            console.log(2)
        }
    }

    Foo.prototype.a = function(){
        console.log(3);
    }

    Foo.a = function(){
        console.log(4);
    }

    Foo.a();
    let obj = new Foo();
    obj.a();
    Foo.a();
</script>
</body>
</html>
